Sean Lennon has teamed up with filmmaker Jordan Galland to write the music for Alter Egos, a forthcoming comedy about superheroes in a setting that resembles real life a bit more than movies, starring the likes of Batman, the X-Men, Iron Man and Spider-Man. (You can watch the trailer for the movie above.) Lennon's soundtrack, a pastiche of familiar superhero movie orchestration and a variety of pop styles, further cements his reputation as a musical chameleon. Lennon chatted with Rolling Stone recently about working on the film, as well as his other projects with his girlfriend, musician and model Charlotte Kemp Muhl.

How did your friend Jordan Galland pitch you on doing the soundtrack for this new movie, Alter Egos?Jordan Galland and I have been working together on various projects and various media since he was 16 or 17. I made the music for his first film – it's called Rosencrantz and Guildenstern Are Undead, it's like a vampire parody sort of inspired by Tom Stoppard's play. He's a very close friend, so working with him is sort of a labor of love, so it's not a job, per se.

This is a movie about real-life superheroes. Did you have a background in superheroes and comic books?Well, I do live a double life. I am actually a comic book enthusiast, but not so much for the DC/Marvel type. I'm more into Chris Ware and Robert Crumb, but I did grow up reading Spider-Man, for sure. I think this movie is sort of the superhero genre film, but it's not really because it's not an action film – it's not about special effects and fancy filming technique. It's a dialogue-driven film. It's sort of like a little comedy.

When you're making a movie that on the surface is one thing, but is actually a different thing tonally, how does that affect your decisions in making the music? Is it up to you to find the right balance, to get both moods across at once?That was really challenging, actually. We went through several versions of the style, or the approach, that we were going to take. At first, we did a kind of goofy, Napoleon Dynamite sort of thing which didn't really work out. It sort of highlighted the wrong aspects of the film. Then there was another direction we went, which was a retro Italian superhero film, kind of a Barbarella direction. I really enjoyed making that music, but it didn't ground the film and it lacked gravity. Despite how silly the film is and how kind of comedic it is, it needed a certain seriousness to sort of propel the more important aspects of the narrative – you know, the parents having been killed by this bad guy and the superhero avenging the murder of his parents. It needed some grounding. That was when we sort of went with the third direction, which was kind of a straight-up action hero style– a serious, orchestrated superhero score.

So what happens with all this music that you've composed but have had to scrap? If you liked it, what do you end up doing with it?Well, funny enough, all the stuff that I've thrown away or discarded or put aside from when I was younger, I still have, because it's all on tape. But since the invention of digital, I pretty much lose everything. There are tons of weird records that I think are just gone because I changed computers or the format changed. There is something very fleeting about digital. Maybe now that I have my own label, I could eventually put out some sort of like the Lost Sean Tapes, or something.

What else have you been working on lately?I have a band called the GOASTT, or the Ghost of a Saber Tooth Tiger is the full name, but we call ourselves the GOASTT. That's with my girlfriend, Charlotte Kemp Muhl, and we've already put out a record called The Acoustic Sessions on Chimera Music, which is my label. I'm also working on producing another band that my girlfriend is in called Kemp and Eden. It's sort of a surrealist folkie girl duo.